A navigation system has a function to detect a current position and a function to retrieve a guide route from the current position to an inputted destination. While the vehicle is traveling, the navigation system displays the guide route and current position on a map in a display screen to navigate the vehicle to the destination. When the vehicle departs from the guide route during the route guidance, the navigation system re-retrieves a route from the current position to the destination using a re-routing function. The vehicle is then navigated based on the re-retrieved route.
In general, when a destination is inputted in the navigation system, an intermediate location can be also inputted. A guide route is retrieved to go though the inputted intermediate position to the destination. Accordingly, a user can designate a route to visit or pass by an intended place (e.g., a scenic location) on the way to a destination by inputting the intended position as an intermediate position.
A conventional navigation system determines that a subject vehicle has passed by an intermediate position only when the subject vehicle has actually passed by a position inputted as the intermediate position. The vehicle may mistake a heading direction to depart from the guide route. In this case, if there is a certain intermediate position which is not determined to be passed by, the re-routing function designates a new guide route to go via the certain intermediate position to the destination.
However, for instance, in the case of mistaking the heading direction, the user may abandon visiting the certain intermediate position and heads for a next intermediate position or destination even though the certain intermediate position was initially intended to visit. Considering the above situation, a navigation system in Patent Document 1 designates a new guide route as follows. When a subject vehicle starts traveling a route different from the guide route to get away from an intermediate position which is not determined to be passed by, the navigation system assumes that the subject vehicle has passed by the intermediate position and designates a new guide route.                Patent Document 1: JP-2000-193478 A        
The above conventional navigation system in Patent Document 1 has another unsolved problem. For instance, assume that a guided route is designated by inputting a store as an intermediate position a user wants to visit on the way to a destination. Since the store has a parking lot a little away from the store, the user drives to the parking lot and walks to the store. After finishing errands at the store, the user backs to the vehicle at the parking lot and starts to drive the vehicle.
In this case, since the store is not arrived at by the vehicle, the navigation system determines that the store as an intermediate position is not passed by or arrived at. The user is therefore guided in a route, which is newly designated to include the store as an intermediate position. The user thinks that he/she has visited the store; the user drives to follow the new guided route without noticing that the vehicle is guided to the store. As the vehicle approaches the store, the user feels strange and then notices that the vehicle is guided to the store, which the user has visited.
Similarly to the case of using the parking lot near the intermediate position, this problem may also arise in the case that a user parks a subject vehicle at a parking lot near a destination and walks to the destination. In this case, when the user re-starts driving the vehicle, the navigation system does not recognize the arrival to the destination and continues guiding the vehicle to the destination, causing the problem.